Página 1 dos resultados de 42979 itens digitais encontrados em 0.027 segundos

Oestradiol Potentiates Hormone Secretion and Neuronal Activation in Response to Hypertonic Extracellular Volume Expansion in Ovariectomised Rats

VILHENA-FRANCO, T.; MECAWI, A. S.; ELIAS, L. L. K.; ANTUNES-RODRIGUES, J.
Fonte: WILEY-BLACKWELL Publicador: WILEY-BLACKWELL
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.43%
Secretion of vasopressin (VP), oxytocin (OT) and atrial natriuretic peptide (ANP) is an essential mechanism for the maintenance of hydromineral homeostasis. Secretion of these hormones is modulated by several circulating factors, including oestradiol. However, it remains unclear how oestradiol exerts this modulation. In the present study we investigated the participation of oestradiol in the secretion of VP, OT and ANP and in activation of vasopressinergic and oxytocinergic neurones of the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus in response to extracellular volume expansion (EVE). For this purpose, ovariectomised (OVX) rats treated for 7 days with vehicle (corn oil, 0.1 ml/rat, OVX+O group) or oestradiol (oestradiol cypionate, 10 mu g/kg, OVX+E group) were subjected to either isotonic (0.15 m NaCl, 2 ml/100 g b.w., i.v.) or hypertonic (0.30 m NaCl, 2 ml/100 g b.w., i.v.) EVE. Blood samples were collected for plasma VP, OT and ANP determination. Another group of rats was subjected to cerebral perfusion, and brain sections were processed for c-Fos-VP and c-Fos-OT double-labelling immunohistochemistry. In OVX+O rats, we observed that both isotonic and hypertonic EVE increased plasma OT and ANP concentrations...

O papel da flagelina e do sistema de secreção de Escherichia coli enteroinvasora na resposta imune inata dos macrófagos; The role of flagellin and secretion system of enteroinvasive Escherichia coli in the immune response innate macrophages

Ferreira, Lucas Gonçalves
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/12/2012 PT
Relevância na Pesquisa
36.47%
Escherichia coli enteroinvasora (EIEC) é um dos agentes etiológicos da disenteria bacilar. Seu processo fisiopatológico é desencadeado pela expressão de fatores de virulência, que proporcionam sua invasão e sobrevivência nas células do hospedeiro, ativando o sistema imune inato e adaptativo da mucosa intestinal. Trabalhos recentes têm salientado a importância do sistema de secreção e da flagelina bacteriana como agonista de receptores da imuninade inata dos macrófagos, em especial alguns dos receptores do tipo NLR. Uma vez que esta espécie de E. coli também é capaz de expressar flagelina e fazer a montagem completa do flagelo e do sistema de secreção do tipo III, a nossa proposta foi avaliar o papel da flagelina e do sistema de secreção de EIEC na resposta imune dos macrófagos murinos. Para isso, utilizamos três cepas de EIEC: a cepa selvagem; a cepa mutante no gene responsável pela síntese da flagelina; e a cepa sem o plasmídio de virulência plnv, deficiente no sistema de secreção, para a infecção de macrófagos peritoniais de camundongos C57BI/6, caspase-1-/-, IPAF-/- e ASC-/-. Neste estudo foi possível observar que o escape bacteriano e a morte dos macrófagos infectados por EIEC, assim como a ativação da caspase-1 e posterior secreção de IL-1β é independente da flagelina bacteriana...

Influência do colesterol e de intermediários da sua biossíntese sobre a maquinaria de secreção de insulina e a organização funcional da membrana plasmática em células secretoras de insulina.; Influence of cholesterol and its biosynthesis intermediates on the insulin secretion machinery and the functional organization of the plasma membrane in insulin secreting cells.

Hertz, Juan Pablo Zúñiga
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/11/2014 PT
Relevância na Pesquisa
36.45%
A rota de biossíntese de colesterol tem sido estudada pelo seu envolvimento com a secreção de hormônios. A secreção de insulina depende do colesterol e de intermediários da sua biossíntese como o geranilgeranil pirofosfato. Para compreender a contribuição destes elementos na secreção de insulina foram utilizados inibidores de diferentes pontos da rota de biossíntese do colesterol. Estudou-se a contribuição do geranilgeranil pirofosfato e do colesterol na secreção de insulina estimulada pela glicose e analisados parâmetros físicos de membrana dos quais decorrem aspectos funcionais da célula beta. Sinvastatina inibiu a secreção de insulina sem afetar o conteúdo celular de colesterol, mas inibindo a geranilgeranilação de proteínas. A diminuição do conteúdo de colesterol aumenta a fluidez de membrana desorganizando lipid rafts. A suplementação com colesterol recupera a função secretória. Por tanto, a inibição da síntese de colesterol diminui a secreção de insulina através da redução da isoprenilação de proteínas e da alteração estrutural de membranas celulares.; Cholesterol biosynthesis pathway has been studied for its involvement with the hormone secretion process. Insulin secretion depends on cholesterol and its biosynthesis intermediates such as geranylgeranyl pyrophosphate. For understand their contribution on the glucose stimulated insulin secretion...

Mechanisms of insulin secretion in malnutrition: modulation by amino acids in rodent models

Machado de Oliveira, Camila Aparecida; Latorraca, Marcia Queiroz; Rostom de Mello, Maria Alice; Carneiro, Everardo Magalhaes
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 1027-1034
ENG
Relevância na Pesquisa
36.45%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Protein restriction at early stages of life reduces beta-cell volume, number of insulin-containing granules, insulin content and release by pancreatic islets in response to glucose and other secretagogues, abnormalities similar to those seen in type 2 diabetes. Amino acids are capable to directly modulate insulin secretion and/or contribute to the maintenance of beta-cell function, resulting in an improvement of insulin release. Animal models of protein malnutrition have provided important insights into the adaptive mechanisms involved in insulin secretion in malnutrition. In this review, we discuss studies focusing on the modulation of insulin secretion by amino acids, specially leucine and taurine, in rodent models of protein malnutrition. Leucine supplementation increases insulin secretion by pancreatic islets in malnourished mice. This effect is at least in part due to increase in the expression of proteins involved in the secretion process, and the activation of the PI3K/PKB/mTOR pathway seems also to contribute. Mice supplemented with taurine have increased insulin content and secretion as well as increased expression of genes essential for beta-cell functionality. The knowledge of the mechanisms through which amino acids act on pancreatic beta-cells to stimulate insulin secretion is of interest for clinical medicine. It can reveal new targets for the development of drugs toward the treatment of endocrine diseases...

Resolução estrutural de proteínas hipotéticas, chaperonas de secreção, da bactéria Xanthomonas axonopodis pv. citri; Structural insights on hypothetical proteins, secretion chaperones from Xanthomonas axonopodis pv. citri

Juliana Fattori
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/09/2011 PT
Relevância na Pesquisa
36.45%
O presente estudo teve por objetivo a caracterização estrutural de quatro possíveis chaperonas de secreção da bactéria Xanthomonas axonopodis pv. citri (Xac). Esta caracterização é importante para entender as funções destas proteínas e consequentemente compreender os mecanismos de virulência da Xac que é a causadora do cancro cítrico. Das quatro proteínas estudadas, a XACb0033 é considerada uma possível chaperona de secreção do sistema de secreção do tipo IV; a XAC1346 são possíveis chaperonas de secreção do sistema de secreção do tipo III e a XAC1990, foi identificada em 2007 como uma proteína do sistema flagelar (FlgN). As quatro proteínas, clonadas em pET23a, foram expressas em E. coli, purificadas e obtidas enoveladas conforme as análises de dicroísmo circular (CD). Por CD também se observou um alto conteúdo helicoidal na estrutura secundária das proteínas. Elas foram caracterizadas por filtração em gel analítica, espectrometria de massas, técnicas de difusão de ressonância magnética nuclear (DOSY-NMR) e espalhamento de raios-X a baixo ângulo (SAXS). Por SAXS obteve-se um modelo do envelope molecular de duas proteínas que foi condizente com a estrutura tridimensional obtida por bioinformática. Baseando-se nos resultados obtidos foi possível especular a classificação da XAC0419 como provável chaperona secretória da classe I e a FlgN (XAC1990) foi classificada como uma chaperona flagelar (classe III); e para a XACb0033 observou-se similaridade estrutural com a VirE1...

Investigation of protein secretion and secretion stress in Ashbya gossypii

Aguiar, Tatiana Quinta; Ribeiro, Orquídea; Arvas, Mikko; Wiebe, Marilyn G.; Penttilä, Merja; Domingues, Lucília
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 18/12/2014 ENG
Relevância na Pesquisa
36.5%
Background: Ashbya gossypii is a filamentous Saccharomycete used for the industrial production of riboflavin that has been recently explored as a host system for recombinant protein production. To gain insight into the protein secretory pathway of this biotechnologically relevant fungus, we undertook genome-wide analyses to explore its secretome and its transcriptional responses to protein secretion stress. Results: A computational pipeline was used to predict the inventory of proteins putatively secreted by A. gossypii via the general secretory pathway. The proteins actually secreted by this fungus into the supernatants of submerged cultures in minimal and rich medium were mapped by two-dimensional gel electrophoresis, revealing that most of the A. gossypii secreted proteins have an isoelectric point between 4 and 6, and a molecular mass above 25 kDa. These analyses together indicated that 1-4% of A. gossypii proteins are likely to be secreted, of which less than 33% are putative hydrolases. Furthermore, transcriptomic analyses carried out in A. gossypii cells under recombinant protein secretion conditions and dithiothreitol-induced secretion stress unexpectedly revealed that a conventional unfolded protein response (UPR) was not activated in any of the conditions...

Prolactin regulates luminal bicarbonate secretion in the intestine of the sea bream (Sparus aurata L.)

Ferlazzo, A.; Carvalho, E. S. M.; Gregorio, S. F.; Power, Deborah; Canario, Adelino V. M.; Tischitta, F.; Fuentes, J.
Fonte: Company of Biologists Publicador: Company of Biologists
Tipo: Artigo de Revista Científica
Publicado em 01/11/2012 ENG
Relevância na Pesquisa
36.47%
The pituitary hormone prolactin is a pleiotropic endocrine factor that plays a major role in the regulation of ion balance in fish, with demonstrated actions mainly in the gills and kidney. The role of prolactin in intestinal ion transport remains little studied. In marine fish, which have high drinking rates, epithelial bicarbonate secretion in the intestine produces luminal carbonate aggregates believed to play a key role in water and ion homeostasis. The present study was designed to establish the putative role of prolactin in the regulation of intestinal bicarbonate secretion in a marine fish. Basolateral addition of prolactin to the anterior intestine of sea bream mounted in Ussing chambers caused a rapid (<20min) decrease of bicarbonate secretion measured by pH-stat. A clear inhibitory dose–response curve was obtained, with a maximal inhibition of 60–65% of basal bicarbonate secretion. The threshold concentration of prolactin for a significant effect on bicarbonate secretion was 10ngml–1, which is comparable with putative plasma levels in seawater fish. The effect of prolactin on apical bicarbonate secretion was independent of the generation route for bicarbonate, as shown in a preparation devoid of basolateral HCO3 –/CO2 buffer. Specific inhibitors of JAK2 (AG-490...

Modulation of hormone secretion by functional electrical stimulation of the intact and incompletely dysfunctional dog pancreas

Rozman,J.; Bunc,M.; Zorko,B.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2004 EN
Relevância na Pesquisa
36.48%
The purpose of the present study was to modulate the secretion of insulin and glucagon in Beagle dogs by stimulation of nerves innervating the intact and partly dysfunctional pancreas. Three 33-electrode spiral cuffs were implanted on the vagus, splanchnic and pancreatic nerves in each of two animals. Partial dysfunction of the pancreas was induced with alloxan. The nerves were stimulated using rectangular, charge-balanced, biphasic, and constant current pulses (200 µs, 1 mA, 20 Hz, with a 100-µs delay between biphasic phases). Blood samples from the femoral artery were drawn before the experiment, at the beginning of stimulation, after 5 min of stimulation, and 5 min after the end of stimulation. Radioimmunoassay data showed that in the intact pancreas stimulation of the vagal nerve increased insulin (+99.2 µU/ml) and glucagon (+18.7 pg/ml) secretion and decreased C-peptide secretion (-0.15 ng/ml). Splanchnic nerve stimulation increased insulin (+1.7 µU/ml), C-peptide (+0.01 ng/ml), and glucagon (+50 pg/ml) secretion, whereas pancreatic nerve stimulation did not cause a marked change in any of the three hormones. In the partly dysfunctional pancreas, vagus nerve stimulation increased insulin (+15.5 µU/ml), glucagon (+11 pg/ml)...

Molecular Motors of ESX-Type Secretion Systems

Ramsdell, Talia Lynn
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
Relevância na Pesquisa
36.47%
Tuberculosis is an enormous global health problem. Despite decades of research, the mechanism(s) by which Mycobacterium tuberculosis (Mtb) mediates virulence remains incompletely understood. The ESX-1 secretion system is critical for Mtb to survive and cause disease in vivo, but its primary function and mechanism of action are unclear. The many inherent challenges of working with this slow-growing pathogen often limit the experimental approaches that can be used to address these questions. Thus, we have developed a model system in the nonpathogenic bacterium Bacillus subtilis to study ESX-type secretion systems. Here, we demonstrate that the B. subtilis yuk operon encodes an ESX-type secretion system responsible for the secretion of YukE. Additionally, we demonstrate that the yuk system is active in B. subtilis during conditions of nutrient deprivation and is required for normal biofilm formation. Interestingly, this is similar to our findings that the Mtb ESX-1 system plays dual roles in protein secretion and modulating cell wall integrity. One defining feature of all ESX loci is the presence of an FtsK/SpoIIIE family ATPase. Interestingly, these ATPases have a domain structure unique to ESX-associated ATPases, where each protein contains multiple (2-3) enzymatic domains. We used our B. subtilis system to dissect the mechanism of action of this unique class of motor proteins. We find that the yuk-encoded ATPase YukBA dimerizes to form a hexamer of enzymatic subunits that are differentially required for secretion. Strikingly...

Monoacylglycerol as a metabolic coupling factor in glucose-stimulated insulin secretion

Zhao, Shangang
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
Relevância na Pesquisa
36.58%
Les cellules beta pancréatiques sécrètent l’insuline lors d’une augmentation post-prandiale du glucose dans le sang. Ce processus essentiel est contrôlé par des facteurs physiologiques, nutritionnels et pathologiques. D’autres sources d’énergie, comme les acides aminés (leucine et glutamine) ou les acides gras potentialisent la sécrétion d’insuline. Une sécrétion d’insuline insuffisante au besoin du corps déclanche le diabète. Le rôle que joue l’augmentation du calcium intracellulaire et les canaux K+/ATP dans la sécrétion d’insuline est bien connu. Bien que le mécanisme exact de la potentialisation de la sécrétion d’insuline par les lipides est inconnu, le cycle Glycérolipides/Acides gras (GL/FFA) et son segment lipolytique ont été reconnu comme un composant essentiel de la potentialisation lipidique de la sécrétion d’insuline. Le diacylglycérol, provenant de la lipolyse, a été proposé comme un signal lipidique important d’amplification. Cependant, l’hydrolyse des triglycérides et des diacylglycérides a été démontrée essentielle pour la sécrétion d’insuline stimulée par le glucose, en suggérant un rôle du monoacylglycérol (MAG) dans ce processus. Dans cette étude...

Untersuchung der Ionentransportmechanismen, die für die Volumenveränderung kultivierter Parietalzellen bei Stimulation der Säuresekretion verantwortlich sind; K+ and Cl- channels mediate shrinkage during stimulation of acid secretion in cultured parietal cells

Heinzmann, Alexander Tobias
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.45%
Untersuchung der Ionentransportmechanismen, die für die Volumenveränderung kultivierter Parietalzellen bei Stimulation der Säuresekretion verantwortlich sind Im Rahmen des Säuresekretionsvorganges der Parietalzelle spielen außer der H+/K+-ATPase noch zahlreiche weitere Ionentransportprozesse eine bedeutende Rolle. In der vorliegenden Arbeit wurden eine Parietalzell-Primärkultur mit den Agonisten der Säuresekretion Forskolin (10-5 M) und Carbachol (10-4 M) stimuliert, um die Änderungen der Säuresekretion und die Volumenveränderungen unter Beeinflussung der verschiedenen Ionentransporter, insbesondere von K+ und Cl- Kanälen, zu beobachten. 293B (10 μM), ein Hemmstoff des KCNQ1 K+ Kanals, führte nicht zur Zellschwellung, verringerte aber die Schrumpfung durch Forskolin stärker als die durch Carbachol. 50 nM ChTX führte ebenfalls nicht zur Zellschwellung, hatte keinen Einfluss auf die Schrumpfung nach Forskolin-Stimulation und blockierte einen Großteil der Carbachol-induzierten Schrumpfung. NPPB (300 μM), ein Cl- Kanalblocker führte ebenfalls nicht zur Schwellung, verhinderte aber die stimulations-assoziierte Zellschrumpfung beider Agonisten nahezu vollständig. Die Hemmung der Säureproduktion durch 293B, ChTX und NPPB folgte dem gleichen Muster wie die Hemmung der initialen Zellschrumpfung nach Stimulation. 10 μM SCH28080...

Einfluss freier Fettsäuren auf die Insulinsekretion beim Menschen; Influence of free fatty acids on insulin secretion in humans

Steigenberger, Mirjam Elisabeth
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.5%
Zu den pathophysiologischen Grundlagen des Diabetes mellitus Typ 2 gehören die Insulinresistenz und die gestörte Insulinsekretion. Ziel dieser Arbeit war es, zu untersuchen, ob der Spiegel der freien Fettsäuren im Nüchternplasma bei Risikopersonen für Diabetes mellitus Typ 2 die Insulinsekretion beeinträchtigt. Hierfür untersuchten wir in einer Querschnittsuntersuchung 1055 Probanden mit positiver Familienanamnese für Typ 2 Diabetes mellitus. Unabhängig von Alter, Geschlecht, Insulinsensitivität und prozentualem Fettgehalt des Körpers fanden wir in unserer multivariaten linearen Regressionsanalyse eine statistisch signifikante negative Korrelation (p<0,0001) der Konzentration nüchtern freier Fettsäuren mit der ersten Phase der Insulinsekretion. Dieser Befund bestätigt Hinweise aus früheren Studien. Aus bisher durchgeführten Studien ging jedoch nicht hervor, ob ein erhöhter Nüchternspiegel freier Fettsäuren die Entwicklung der ersten Phase der Glukose-induzierten Insulinsekretion beeinflusst oder voraussagen kann. Außerdem war bisher unklar inwiefern der Nüchternspiegel der freien Fettsäuren und die Änderung der ersten Phase der Glukose-induzierten Insulinsekretion durch eine Lebensstiländerung beeinflusst werden können. Zu diesem Zweck untersuchten wir bei 105 Probanden mit positiver Familienanamnese für Typ 2 Diabetes mellitus den Nüchternspiegel freier Fettsäuren und im Rahmen eines oralen Glukosetoleranztests die erste Phase der Insulinsekretion vor und nach einer 9-monatigen Lebensstilintervention. Außerdem wurden anthropometrische und metabolische Parameter erhoben...

Étude dans la cellule bêta pancréatique de voies inhibitrices de la sécrétion d'insuline liées au métabolisme des lipides

Pepin, Émilie
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.58%
Le diabète de type 2 (DT2) est une maladie métabolique complexe causée par des facteurs génétiques mais aussi environnementaux, tels la sédentarité et le surpoids. La dysfonction de la cellule β pancréatique est maintenant reconnue comme l’élément déterminant dans le développement du DT2. Notre laboratoire s’intéresse à la sécrétion d’insuline par la cellule β en réponse aux nutriments calorigéniques et aux mécanismes qui la contrôle. Alors que la connaissance des mécanismes responsables de l’induction de la sécrétion d’insuline en réponse aux glucose et acides gras est assez avancée, les procédés d’inhibition de la sécrétion dans des contextes normaux ou pathologiques sont moins bien compris. L’objectif de la présente thèse était d’identifier quelques-uns de ces mécanismes de régulation négative de la sécrétion d’insuline dans la cellule β pancréatique, et ce en situation normale ou pathologique en lien avec le DT2. La première hypothèse testée était que l’enzyme mitochondriale hydroxyacyl-CoA déshydrogénase spécifique pour les molécules à chaîne courte (short-chain hydroxyacyl-CoA dehydrogenase, SCHAD) régule la sécrétion d’insuline induite par le glucose (SIIG) par la modulation des concentrations d’acides gras ou leur dérivés tels les acyl-CoA ou acyl-carnitine dans la cellule β. Pour ce faire...

Étude de l'implication des navettes du pyruvate découlant du métabolisme mitochondrial du glucose dans la régulation de la sécrétion d'insuline par les cellules bêta pancréatiques

Guay, Claudiane
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.6%
Le diabète est une maladie métabolique qui se caractérise par une résistance à l’insuline des tissus périphériques et par une incapacité des cellules β pancréatiques à sécréter les niveaux d’insuline appropriés afin de compenser pour cette résistance. Pour mieux comprendre les mécanismes déficients dans les cellules β des patients diabétiques, il est nécessaire de comprendre et de définir les mécanismes impliqués dans le contrôle de la sécrétion d’insuline en réponse au glucose. Dans les cellules β pancréatiques, le métabolisme du glucose conduit à la production de facteurs de couplage métabolique, comme l’ATP, nécessaires à la régulation de l’exocytose des vésicules d’insuline. Le mécanisme par lequel la production de l’ATP par le métabolisme oxydatif du glucose déclenche l’exocytose des vésicules d’insuline est bien décrit dans la littérature. Cependant, il ne peut à lui seul réguler adéquatement la sécrétion d’insuline. Le malonyl-CoA et le NADPH sont deux autres facteurs de couplage métaboliques qui ont été suggérés afin de relier le métabolisme du glucose à la régulation de la sécrétion d’insuline. Les mécanismes impliqués demeurent cependant à être caractérisés. Le but de la présente thèse était de déterminer l’implication des navettes du pyruvate...

Rôle de l'estérification des acides gras dans la régulation de la sécrétion d'insuline et le stress métabolique induits par le glucose

Barbeau, Annie
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.59%
Le diabète est une maladie chronique de l’homéostasie du glucose caractérisée par une hyperglycémie non contrôlée qui est le résultat d’une défaillance de la sécrétion d’insuline en combinaison ou non avec une altération de l’action de l’insuline. La surnutrition et le manque d’activité physique chez des individus qui ont des prédispositions génétiques donnent lieu à la résistance à l’insuline. Pendant cette période dite de compensation où la concentration d’acides gras plasmatiques est élevée, l’hyperinsulinémie compense pleinement pour la résistance à l’insuline des tissus cibles et la glycémie est normale. Le métabolisme du glucose par la cellule pancréatique bêta entraîne la sécrétion d’insuline. Selon le modèle classique de la sécrétion d’insuline induite par le glucose, l’augmentation du ratio ATP/ADP résultant de la glycolyse et de l’oxydation du glucose, induit la fermeture des canaux KATP-dépendant modifiant ainsi le potentiel membranaire suivi d’un influx de Ca2+. Cet influx de Ca2+ permet l’exocytose des granules de sécrétion contenant l’insuline. Plusieurs nutriments comme les acides gras sont capables de potentialiser la sécrétion d’insuline. Cependant...

Calnuc plays a role in dynamic distribution of Gαi but not Gβ subunits and modulates ACTH secretion in AtT-20 neuroendocrine secretory cells

Lin, Ping; Fischer, Thierry; Lavoie, Christine; Huang, Haining; Gist Farquhar, Marilyn
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artículo Formato: 3935576 bytes; application/pdf
ENG
Relevância na Pesquisa
36.47%
16 pages, 11 figures; In AtT-20 cells ACTH secretion is regulated by both Ca2+ and G proteins. We previously demonstrated that calnuc, an EF-hand Ca2+ binding protein which regulates Alzheimer's β-amyloid precursor protein (APP) biogenesis, binds both Ca2+ as well as Gα subunits. Here we investigate calnuc's role in G protein-mediated regulation of ACTH secretion in AtT-20 neuroendocrine secretory cells stably overexpressing calnuc-GFP. Similar to endogenous calnuc, calnuc-GFP is mainly found in the Golgi, on the plasma membrane (PM), and associated with regulated secretion granules (RSG). By deconvolution immunofluorescence, calnuc-GFP partially colocalizes with Gαi1/2 and Gαi3 at the PM and on RSG. Cytosolic calnuc(ΔSS)-CFP with the signal sequence deleted also partially colocalizes with RSG and partially cosediments with Gαi1/2 in fractions enriched in RSG. Overexpression of calnuc-GFP specifically increases the distribution of Gαi1/2 on the PM whereas the distribution of Gβ subunits and synaptobrevin 2 (Vamp 2) is unchanged. Overexpression of calnuc-GFP or cytosolic calnuc(ΔSS)-CFP enhances ACTH secretion two-fold triggered by mastoparan or GTPγS but does not significantly affect glycosaminoglycan (GAG) chain secretion along the constitutive pathway or basal secretion of ACTH. Calnuc's facilitating effects on ACTH secretion are decreased after introducing anti-Gαi1/2...

Roles of Cftr-dependent Fluid Secretion During Organ Morphogenesis and Function

Navis, Adam
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2014
Relevância na Pesquisa
36.45%

Fluid secretion is essential to organ development and function, yet relatively little is known about the roles of fluid secretion in vivo. Early in development, fluid secretion plays important roles during the process of lumen formation and is necessary for organ homeostasis throughout life. A human disease, cystic fibrosis (CF) is caused by loss of cystic fibrosis transmembrane conductance regulator (CFTR) function, a chloride channel and key regulator of vertebrate fluid secretion. CFTR regulates fluid secretion by governing ion transport and osmotic gradients across epithelia.

To identify the developmental requirements for cftr function, we generated cftr mutant zebrafish using transcription activator like effector nucleases (TALENs). In cftr mutant zebrafish, we observed defects in the specification of left-right (LR) asymmetry. In the zebrafish, LR asymmetry is specified in part by directional fluid flow within a ciliated structure, Kupffer's vesicle (KV). Using live imaging of several transgenic markers in KV, we determined that lumen expansion is impaired in cftr mutants, which prevents directional fluid flow necessary for KV function. To examine cftr expression...

The Chlamydia Trachomatis Protein Interaction Network: Insights into the Unique Composition of the Type Three Secretion System

Spaeth, Kris Edmund
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 2922617 bytes; application/pdf
Publicado em 19/11/2008 EN_US
Relevância na Pesquisa
36.49%

The Gram-negative bacteria Chlamydia trachomatis is a common sexually transmitted pathogen that can cause severe sequelae including cause pelvic inflammatory disease and sterility. This obligate intracellular pathogen effectively manipulates host cellular functions by secreting virulence factors across its membrane bound vacuole. Identifying these virulence components and how they help in establishing an environment conducive for bacterial growth is central to understanding chlamydial pathogenesis. This is experimentally challenging due to a lack of tools to perform molecular genetic studies. In the absence of genetic tools, we developed a yeast model system to identify and characterize chlamydial proteins involved in virulence mechanisms. In this study we describe the identification of twenty-eight proteins potentially involved in modulating host cellular functions and the secretion of virulence factors into the host. Since the delivery of virulence proteins by a type three secretion (T3S) system is a critical step for Chlamydia, we identified the proteins that interacted with the T3S apparatus by yeast two-hybrid analysis. We discovered several novel interactions between and determined that the C. trachomatis T3S apparatus displayed a similar architecture to that of other T3S systems. Furthermore with these approaches we identified networks of proteins that interacted with the secretion apparatus including a novel secretion chaperone protein. We characterized Ct260/Mcsc one of the putative secretion and demonstrated that it represents a novel class 1B secretion chaperone protein. Unlike other known chaperones...

Secretion and Lipopolysaccharide Binding of Heat-Labile Enterotoxin

Mudrak, Benjamin
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 2999594 bytes; application/pdf
Publicado em //2010 EN_US
Relevância na Pesquisa
36.47%

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of morbidity and mortality worldwide. The causative agent of traveler's diarrhea, ETEC is often associated with cholera-like disease, especially in developing countries. One major virulence factor released by ETEC is the heat-labile enterotoxin LT, which upsets the balance of electrolytes in the intestine. LT is highly similar to cholera toxin (CT) produced by Vibrio cholerae, both in structure and function. The toxin consists of a single catalytically active A subunit and a ring of five B subunits mediating its binding and secretion. Previous work from our lab has shown that, after export by the type II secretion (T2S) system, LT associates with lipopolysaccharide (LPS) on the bacterial surface. However, little is known about what identifies LT as a T2S substrate, and the portion of the toxin that mediates LPS binding has not previously been defined. Site-directed mutagenesis of residues in a peripheral sugar binding pocket of the toxin was performed, revealing mutations that affect its binding to LPS, as determined by an in vitro cell surface binding assay. One binding mutant, which is expressed and secreted at wild-type levels from ETEC...

Computational and experimental approaches to enhance extracellular secretion of recombinant proteins in Escherichia coli

Agarwal, Anup
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
36.5%
Lee, Kelvin; The annual global market for biopharmaceuticals is estimated at about $99 billion. Approximately 40% of all biotechnology products made in the US and EU are derived from Escherichia coli expression systems. Thus, efforts to study and improve E. coli as the host microorganism for the production of recombinant proteins can be of considerable importance. Secretion of recombinant proteins into the extracellular medium via the Type-I secretion system (TISS) in E. coli offers several advantages in comparison to the cytoplasmic accumulation and the periplasmic secretion such as simplifying detection and purification of the target protein and also providing a better folding environment. Studies have shown that the premature termination of the RutR protein, a transcription factor encoded by the ycdC gene, can enhance the secretion levels of recombinant proteins via the TISS. Here, the construction of an E. coli ΔycdC strain is described that enhances the extracellular levels of α-hemolysin (HlyA) and GILL-β- lactamase (GILL-Bla) (3.03-fold) proteins via the TISS. Previous experiments have shown that synonymous rare codon substitutions in the parent gene sequence can enhance the extracellular levels of multiple proteins via the TISS. Here...